1. Field of the Invention
The present invention relates to a radio communication device having a case, and more particularly to a radio communication device that allows an improved antenna gain even with a reduced antenna mounting space inside a case.
2. Description of the Related Art
In recent years, due to increased functionality of cellular telephones and other radio communication devices, high-density mounting inside the cases is advancing. In particular, in a case of a radio communication device with a case that can be folded, high-density mounting has become remarkable.
Japanese patent laid-open publication JP 09-326632 A (laid open on Dec. 16, 1997) discloses a technique relating to an inverted-F antenna arranged on a conducting plane, and to a passive element arranged parallel to the inverted-F antenna.
Japanese patent laid-open publications JP 10-032424 A (laid open on Feb. 3, 1998), JP 11-340731 A (laid open on Dec. 10, 1999), and JP 2000-216628 A (laid open on Aug. 4, 2000) disclose techniques related to a radio communication device antenna and a passive antenna arranged near this antenna.
However, in antenna apparatuses that are mounted inside their cases, the higher-density mounting in the radio communication device makes it difficult to secure enough mounting space. When the mounting space is reduced, there is a basic tendency that the antenna efficiency and the frequency bandwidth of the antenna device will suffer. Therefore, as the mounting becomes denser and the antenna apparatus mounting space becomes smaller, this causes deterioration of various antenna characteristics.